Respond Real HTTP status code in custome error page

Global.asax.cs

using System;
using System.Configuration;
using System.Web;
using System.Web.Configuration;

public class MvcApplication : System.Web.HttpApplication
{
    public override void Init()
    {
        base.Init();
        this.PreSendRequestHeaders += MvcApplication_PreSendRequestHeaders;
    }

    void MvcApplication_PreSendRequestHeaders(object sender, EventArgs e)
    {
        var app = sender as HttpApplication;
        var err = app.Server.GetLastError() as HttpException;
        if (err != null)
        {
            var customErrors = ConfigurationManager.GetSection("system.web/customErrors") as CustomErrorsSection;
            if (customErrors != null && customErrors.RedirectMode == CustomErrorsRedirectMode.ResponseRewrite)
            {
                var response = app.Context.Response;
                response.StatusCode = err.GetHttpCode();
                response.TrySkipIisCustomErrors = true;
            }
        }
    }
}